The present invention relates to a micro-adjustment mechanism for adjusting installation angle of the spindle motor in an optical disk player, i.e. CD-ROM, CD-player, CD-R, CD-RW, DVD-ROM and DVD-player.
The following technical information may be further referred to in order to have an in-depth understanding of the background and prior art technology regarding the invention.
1. International Standard ISO/IEC 10149, first edition, 1989-09-01, Global Engineering Documents, Irvine, Calif. 92714, USA.
2. Small Form Factor Committee, Specification of ATA Packet Interface for CD-ROM""s, SFF-8020, Revision 1.2, Feb. 24, 1994.
3. SCSI-2 draft proposed American National Standard, Revision 10c. 
4. Red book, Compact Disc-Digital Audio(CD-DA), by Sony Corp. and Philips N. V., April 1987.
5. Yellow book, Compact Disc-Read Only Memory (CD-ROM), by Sony Corp. and Philips N. V., Nov. 1988.
It is well known that there are multiple distinctive servo loops employed in a disk player to reproduce data by guiding the laser beam over the data track through track-search, in-track-following, and focus operations. The prior art servo control system for the optical disk player includes U.S. Pat. Nos. 4,485,337, 4,783,774, 5,289,097, 5,246,479, 5,257,252, 5,345,347, 5,808,978, 5,751,680, 5,796,707 and 5,001,690.
The Red Book mentioned above requires the pitch of disk data tracks to be 1.6 xcexcm and 0.74 xcexcm respectively for CD-ROM and DVD. The in-track-following error of the optical pickup must be within 0.1 xcexcm for CD-ROM and within 0.022 xcexcm for DVD to assure a normal data read/write operation. As an example, for a disk with a diameter of 120 mm, the allowable traverse distance for the pickup during data access operation is 3.5 cm. In order to achieve the long distance movement and precision positioning requirements for the pickup, typical pickup is controlled by a dual-actuator system. That is, one in-track-following actuator is responsible for in-track-following operation, which is in nature of high frequency and short distance movement, and another actuator is responsible for search track operation which is in nature of low frequency and long distance movement. Furthermore, the allowable eccentricity is +200 xcexcm and xe2x88x92200 xcexcm for CD-ROM, and +100 xcexcm and xe2x88x92100 xcexcm for DVD. Despite the operation speed, the servo control for the in-track-following operation must always overcome the existing eccentricity of the disk and/or the physical damage over the surface and, at the same time, keep the in-track-following error within the allowable range (0.1 xcexcm). Theoretically, to accurately reproduce the data on the track, the laser beam radiating from the source must be incident upon the surface of the disk vertically. If there is a minor incident angle error, one denotes it as the optical axis tilt angle. As the track data density and spin speed of the player, e.g. DVD, increase substantially, the existence of the tilt angle would affect the quality and reliability of data reproduction.
As shown in FIG. 1, the optical disk player includes a pickup traverse 10 connected to the loading module (not shown) through four positioning screws (not shown), and is tiltable with respect to the loading module. On the traverse 10, there is provided a spindle 16, which spins in high speed when operated, a turntable 18 and a pickup 12, which is capable of making rectilinear reciprocal movement.
During rectilinear reciprocal movement of the pickup 12, the first guide rail 14 supports and guides the pickup 12. The second guide rail 15 is responsible for the supporting in the horizontal direction to prevent the falling of pickup 12 with respect to axis of the first guide rail 14. During the data reproduction operation of pickup 12, the supporting function of the first guide rail 14 and the second guide rail 15 defines an optical pickup surface along which the pickup 12 moves. The disk 13 sits on the turntable 18 and spins accordingly. During rotation of the disk 13, it defines a spin surface. In theory, to achieve a best data reproduction result, the spin surface should parallel the optical pickup surface. As such, the light beam from the pickup 12 may then be vertically incident to the disk surface and makes the incline angle to be ideally zero regardless of which data track is selected.
Referring to FIG. 2, the optical pickup 12 is movably supported on a feeder 21. The feeder 21 is driven by the actuator 11 in a well-known manner so that optical pickup 12 moves radially in reference to the surface of the optical disk 13. The optical pickup 12 includes a carriage 121, a source of a light beam, e.g., a semiconductor laser device 122, a collimator lens 123, a semi-transparent mirror 124, a device for placing a laser beam on the optical disk 13, e.g., an objective lens 125, a split photosensor 126, an in-track-following actuator 127 and a focusing actuator 128. The laser device 122 radiates the laser beam. The collimator lens 123, the semi-transparent mirror 124 and the objective lens 125 guide the laser beam to the optical disk 13 so that the laser beam is placed on the optical disk 13 in a form of light spot. The optical pickup 12 then scans concentric tracks of the optical disk 13 one after another or a spiral track of the optical disk 13 with the light spot of the laser beam moving in radial direction during the disk information reproduction operation. The laser beam is reflected by the optical disk 13 and then applied to the split photosensor 126 through the objective lens 125 and the semi-transparent mirror 124. The split photosensor 126 detects from the reflected laser beam information data responding to a state, e.g., a strength of the reflected laser beam, and produces an electrical signal responding to the information. The objective lens 125 is movably mounted on the carriage 121 of the optical pickup 12. The in-track-following actuator 127 controls position of objective lens 125 in the radial direction of the disk 13 so that the light spot of the laser beam follows a center of a prescribed track. The tracking control of the objective lens 125 may be made by a conventional tracking control system. The focusing actuator 128 controls the position of objective lens 125 in the perpendicular direction to the surface of the optical disk 13 so that the light spot of the laser beam is accurately focused on a prescribed track. The focusing control of the objective lens 125 may be made by a conventional focusing control system.
Based on the requirement mentioned above, the main objective of the invention is to reduce the incline or elevation angle of the optical axis of the pickup to substantial zero and therefore obtain a reliable high speed data reproduction.
A micro-adjustment apparatus for the spindle motor installation angle in an optical disk player is provided. The optical disk player includes a traverse, and the traverse includes a pickup, a first guide rail, and a framework. The pickup includes a light source for supplying a light beam, and the first guide rail guiding the pickup during data reproduction. A spin surface is defined while the spindle is spinning.
The micro-adjustment apparatus includes a supporting plate, a pivotal device, a first adjustable pivotal device, and a second adjustable pivotal device.
The supporting plate supports the spindle motor and is adjustably coupled to the framework.
The pivotal device is disposed at a first predetermined location on the supporting plate and contacts with the first guide rail.
The first adjustable pivotal device is disposed at a second predetermined location on the supporting plate for adjusting an elevation angle of the supporting plate such that the light beam is substantially vertical to the spin surface.
The second adjustable pivotal device is disposed at a third predetermined location on the supporting plate for adjusting an incline angle of the supporting plate such that the light beam is substantially vertical to the spin surface.